This application is based on and claims priority under 35 U.S.C. xc2xa7119 with respect to German Application No. 100 23 325.2 filed on May 12, 2000, the entire content of which is incorporated herein by reference.
The invention relates to a device for sealing edge areas of an endless, running conveyor belt made of magnetizable material, particularly steel, against which a liquid or gaseous heat exchange medium effects the backside of the belt in the area of a temperature-controlled section. The conveyor belt has at least one interconnected seal arrangement arranged adjacent each lateral edge area and along at least the length of the temperature-controlled section.
U.S. Pat. No. 5,277,246 discloses a running conveyor belt made of steel. In the area of a temperature-controlled section of the conveyor belt, for instance a cooling section, cooling water is sprayed as a heat exchange medium against the underside of the belt whereby products disposed on the belt surface may be cooled. To prevent transverse escaping of the cooling water past the downwardly facing longitudinal edges of the conveyor belt, which could moisten the belt surface in an undesirable manner, seal arrangements in the form of stationary sealing strips are arranged along the longitudinal edge areas of the conveyor belt whereby the longitudinal edge areas of the conveyor belt rest slidably against said sealing strips. The top surfaces of the sealing strips facing the longitudinal edge areas of the conveyor belt are provided with diagonally running grooves. Thereby there is prevented, on one hand, an escape of cooling fluid from the sides of the conveyor belt. On the other hand, cooling fluid adhering to the underside of the belt is returned to the inside by a hydrodynamic action based on the belt movement whereby the need for additional sealing measures is avoided. The sealing strips with their grooves are characterized therefore as hydrodynamic water guides.
It is the object of the invention to further improve the sealing of the underside of a conveyor belt.
This object is achieved in that a magnet structure is provided adjacent at least one of the longitudinal edges for attracting the belt and the respective seal structure together. Preferably, a magnet structure is attached to each seal structure, which magnet structure exerts a uniform attraction force against the conveyor belt along the entire length of the temperature control section. This solves a problem involving thermal or mechanical warping which results in undulated edges on the conveyor belt, whereupon there is no longer a sufficient sealing function. By means of the additionally created magnetic force, it is possible according to the invention, to guarantee sealing of the longitudinal edge areas of the underside of the belt and even in the area of such undulations on the edge of the belt. A continuous seal arrangement may thereby be provided along the entire processing length on each side of the belt, respectively. Alternatively, the respective seal arrangement may extend only along the whole length of the respective temperature-controlled section.
In particular, there may be provided a continuous seal arrangement at each side of the belt, respectively, while an additional seal arrangement is provided for a first cooling or heating section at each side of the belt along the length of an additional cooling or heating section and adjacent to the first cooling or heating section. The entire processing length of the conveyor belt defines the total length of the respective belt strip between a front and a rear return roller for the conveyor belt.
In an embodiment of the invention, each seal arrangement can be designed with diagonally running grooves in the top surface facing the underside of the belt to define a hydrodynamic water guide. In this embodiment, the inventive solution is combined with the solution disclosed in U.S. Pat. No. 5,277,246 whereby further improved sealing is achieved.
At least one seal arrangement may be basically designed in a manner already known from the (current) state-of-the-art. However, especially suitable for the inventive solution are seal arrangements which provide a good support function for the longitudinal edge areas by a somewhat larger bearing surface for said edge areas since the magnetic force of at least one magnet unit may be practically employed only then when at the same time a secure, wide and uniform belt support is available.
In an additional embodiment of the invention, the seal arrangement is provided with at least one channel for guidance of a heat exchange medium for active temperature control for the sidewall areas of the conveyor belt. Especially advantageous is a seal arrangement made of heat-conducting material to achieve a good heating or cooling temperature for the edge areas of the conveyor belt.
In a further embodiment of the invention, the magnet unit is made of a plurality of magnet elements oriented longitudinally in the direction of the belt movement whereby said magnet elements are arranged in a row, one behind the other along the seal arrangement. Cube-shaped or block-shaped magnetic elements may be provided as permanent magnets therefor, for example, so that simple assembly is made possible.
In an additional embodiment of the invention, the magnet unit has at least one electromagnet. This embodiment has the advantage that there is no permanent magnetic effectxe2x80x94only a magnetic effect according to demand.
In an additional embodiment of the invention, the magnet unit is designed to provide a variable magnetic force so that magnetic forces of varying size may act upon the conveyor belt. Thereby, the necessary magnetic force may be variably adjusted according to the corresponding belt dimensions and to the size of the undulations of the belt edges.
In an additional embodiment of the invention, the magnet unit is positioned by means of a height adjustment device in the seal arrangement. Thereby it is possible to employ permanent magnet elements and still exert magnetic forces of varying magnitude onto the conveyor belt.
In an additional embodiment of the invention, at least one electromagnet is connected to a control unit, which controls the electromagnet electrically or electronically in such a manner that said electromagnet exerts magnetic forces of varying magnitude against the conveyor belt. These electric or electronic solutions may be advantageously coupled with belt controls so that a dependence of magnetic forces is made possible in relation to the running belt speed, the belt temperature, or other reference quantities of the belt structure.
In an additional embodiment of the invention, a demagnetizing device is arranged in the direction of the belt movement and behind the temperature-controlled section of the conveyor belt. By demagnetizing the belt, there is less tendency for the belt to magnetically attract metallic particles in the air which could build-up on and foul the belt. The demagnetizing device may be disposed exclusively at the level of the edge areas of the conveyor belt and could take the place of at least one downstream magnet unit. The demagnetizing device may be disposed either directly behind a temperature-controlled section, in the area of the belt discharge area, or also in the area of the returning belt section.